The invention resides in a method for determining the concentration of glucoraphanin in a plant wherein:    a) a sample of the plant is provided,    b) the sample is contacted by a polar non-charged organic solvent and so comminuted that glucoraphanin and further plant material contained in the sample is dissolved in the solvent and    c) from the extract obtained in this way plant parts are removed to clear the extract.
Further, the invention concerns a method for determining the concentration of bio-available sulforaphane in a plant wherein the plant contains glucoraphanin and a splitting enzyme which is spatially separated therefrom and wherein the plant forms sulforaphane when the splitting enzyme comes into contact with the glucoraphanin.
Such a method for determining the concentration of glucoraphanin is known in practice. Herein, a sample of plant to be examined is provided and is comminuted in an acetone-containing solvent in such a way that glucoraphanin contained in the sample is dissolved in the solvent. Subsequently, the extract obtained thereby is first cleared and cleaned. Then a liquid chromatography is performed wherein the extract is moved under high pressure through a column. Along the column various molecules contained in the extract are separated from one another. The column is irradiated by UV light which is absorbed by the molecules. The presence of the glucoraphanin molecules at a predetermined location of the column is detected by an optical sensor which is sensitive in the UV range. The glucoraphanin molecules are then quantified in a further method step by mass spectrometry.
The known method is used in particular for the examination of broccoli cress or respectively broccoli sprouts. Broccoli cress has a high content of glucoraphanin and also contains a splitting enzyme which is spatially separated from the glucoraphanin and which comes into contact with the glucoraphanin when the plant is damaged. Hereby the glucoraphanin is split into sulforaphane and a sugar rest. Basically, the sulforaphane serves to keep pests away from the plant. Examinations have shown that foods which contain sulforaphane in a sufficient concentration are also helpful for the human health. Therefore broccoli cress is used preferably for medical studies. In order to ensure that studies are comparable, the concentration of the glucoraphamine and, in particular, the concentration of the bio-available sulforaphane present in the broccoli cress must be known accurately. Herein the concentration of the bio-available sulforaphane is understood to be the concentration of the sulforaphane which can be formed by the plant itself when the glucoraphanin contained in the plant comes into contact with the splitting enzyme which is also contained in the plant.
The known method of determining the concentration of the glucoraphanin has the disadvantage that its performance is complicated and time-consuming and that large apparatus are required which are generally present only in a suitably equipped laboratory. It is a further disadvantage that the required analysis apparatus require maintenance and also require qualified personal for performing the testing. A method for determining the concentration of bio-available sulforaphane of the type mentioned earlier is not known as far as the applicant knows.
It is therefore the object of the present invention to provide a method of the type described above, whereby the concentration of glucoraphanin in a plant can be determined in a simple manner. A further object of the invention is to provide a method which facilitates a simple determination of the concentration of bio-available sulforaphane in a plant.